Dihydrooxadiazinones and method for making

ABSTRACT

Dihydrooxadiazinones are provided which can be used as blowing agents in various thermoplastic polymeric materials to produce high performance thermoplastic foams. A ketone having at least one α-hydrogen atom is halogenated and hydroxylated to produce an α-hydroxyketone. Condensation of the α-hydroxyketone with an organocarbazate produces the corresponding carboorganooxyhydrazone which is cyclized to a dihydrooxadiazinone.

This application is a continuation-in-part application of copendingapplication Ser. No. 608,450, filed Aug. 28, 1975, now U.S. Pat. No.4,097,671 granted June 27, 1978, and assigned to the same assignee asthe present invention.

The present invention relates to dihydrooxadiazinones, namely3,6-dihydro-1,3,4-oxadiazin-2-ones, and a method for making suchmaterials. There is also included by the present invention a method forhalogenating certain ketones having a α-hydrogen atom and a method ofhydroxylating certain α-halo ketones to produce the correspondingα-hydroxy ketone.

The dihydrooxadiazinones provided by the method of the present inventionare included by the formula, ##STR1## where "a" is an integer equal to 1or 2 and R is monovalent when "a" is 1, and R is divalent when "a" is 2,and R is selected from aryl, alkoxy aryl, haloaryl, nitroaryl andsulfoaryl and correspondingly arylene, alkoxyarylene, haloarylene,nitroarylene and sulfoarylene, and R¹ and R² are monovalent or divalentradicals which can be the same or different selected from hydrogen,alkyl, alkylene, a cyclo aliphatic ring structure including R¹ and R²,alkoxy radicals, aryl and aryloxy radicals, etc.

Radicals included by R of formula (1) are aryl radicals such as phenyl,tolyl, xylyl, naphthyl, anthryl, etc.; C.sub.(1-8) alkoxy aryl such asmethoxyphenyl, ethoxytolyl, etc., halo aryls such as chlorophenyl,bromotolyl, etc.; nitro phenyl and sulfotolyl, etc., phenylene,xylylene, naphthylene, etc. Radicals included by R¹ and R² are hydrogen,and C.sub.(1-8) alkyl radicals such as methyl, ethyl, propyl, etc.;alkoxy radicals such as methoxy, ethoxy, propoxy, butoxy, etc.; arylradicals such as phenyl, tolyl, naphthyl, etc.; aryloxy radicals such asphenoxy, cresoxy, naphthoxy, etc. In particular instances where R¹ andR² are both alkyl they can be part of a cycloaliphatic ring structuresuch as cyclopentyl, cyclohexyl, cycloheptyl.

As shown in my copending application Ser. No. 669,028, filed Mar. 22,1976, now U.S. Pat. No. 4,097,425 granted June 27, 1978, and assigned tothe same assignee as the present invention, the dihydrooxadiazinones offormula (1) can be employed as blowing agents in a variety ofthermoplastic organic polymers. Included by the dihydrooxadiazinones offormula (1) are, for example,

5,6-dimethyl-3,6-dihydro-1,3,4-oxadiazin-2-one,

5,6,6-trimethyl-3,6-dihydro-1,3,4-oxadiazin-2-one,

5-ethyl-6-methoxy-3,6-dihydro-1,3,4-oxadiazin-2-one,

5,6-diphenyl-3,6-dihydro-1,3,4-oxadiazin-2-one,

5-(p-bromophenyl)-3,6-dihydro-1,3,4-oxadiazin-2-one,

5-phenyl-6-methyl-3,6-dihydro-1,3,4-oxadiazin-2-one,

5,6-bis(p-methoxyphenyl)-3,6-dihydro-1,3,4-oxadiazin-2-one,

5-naphthyl-3,6-dihydro-1,3,4-oxadiazin-2-one,

5-(o,o,p-tribromophenyl)-6-propyl-3,6-dihydro-1,3,4-oxadiazin-2-one,

5-(p-hydroxyphenyl)3,6-dihydro-1,3,4-oxadiazin-2-one,

5-phenyl-6,6-cyclopentylene-3,6-dihydro-1,3,4-oxadiazin-2-one,

and such polycyclic formulas resulting from divalent substitution as##STR2##

Also included by the present invention, are a particular class ofdihydrooxadiazinones within the scope of formula (1), and further shownby the following formula, ##STR3## where R³ is an aryl radical, aryleneradical or substituted aryl radical, or substituted arylene radical,such as phenyl, phenylene, chlorophenyl, tolyl, sulphonated naphthyl,etc. The dihydrooxadiazinones of formula (2) are shown in my copendingapplication Ser. No. 669,028, filed Mar. 22, 1976, now U.S. Pat. No.4,097,425, and assigned to the same assignee as the present invention.Included by formula (2) is 5-phenyl-3,6-dihydro-1,3,4-oxadiazin-2-one,which is especially useful as a high temperature blowing agent inthermoplastic organic polymers such as polycarbonates. Based on priorart procedures, certain dihydrooxadiazinones can be made by thecondensation of an α-ketol such as benzoin with equimolar quantities ofcarbethoxy hydrazine to produce a carbethoxy hydrazone followed bycyclization as shown by the following reaction sequence: ##STR4##

The synthesis and pyrolysis of dihydrooxadiazinones have beenextensively reported by M. Rosenblum et al., "Synthesis ofDihydrooxadiazinones and Study of Geometrical Isomerism inα-Ketocarboxyhydrazones", Volume 85, P. 3874 (1963), J. Amer. Chem. Soc.In addition to discussing the use of oxadiazinones as research tools inpyrolysis studies, Rosenblum et al show the synthesis of thedihydrooxadiazinones from α-ketols. Also described by Rosenblum et al isthe employment of a carbethoxy hydrazine to produce the correspondingcarbethoxy hydrazone. The synthesis of the dihydrooxadiazinones by theaforementioned procedure of Rosenblum et al is somewhat limited by theavailable α-ketols as source materials. Current procedures for makingα-ketols are generally based on the hydroxylation of the correspondingα-halo ketone which is derived from ketone possessing an α-hydrogenatom. However, the procedures available in the prior art are generallyundesirable yield wise for both the synthesis of α-halo ketones and thehydroxylation of the α-halo ketones to the α-ketol.

One feature of the present invention, therefore, is directed to theproduction of α-halo ketones by the halogenation of ketones havingα-hydrogen atoms. Prior to the present invention, halogenation ofketones containing α-hydrogen atoms was generally achieved byhalogenating the ketone in the presence of a Lewis acid catalyst.Although this procedure was effective, it invariably resulted in theproduction of polyhalogenated products instead of the exclusiveproduction of the monohalogenated product. A procedure is described byCooper and Davidson, Org. Syn. Coll., Vol. 2, 480 (1943) showing thebromination of acetophenone in diethyl ether with aluminum chloride. Atbest, a mixture is obtained consisting of only 81.8 mole percent of thedesired α-bromoacetophenone and 14.2 mole percent of polybrominatedreaction products along with 4.1 mole percent of unreacted acetophenone.This mixture must be purified by recrystallization which introduces aconsiderable loss in isolated yield. As a result, the overall economicsof available bromination reactions renders these procedures undesirable.

One aspect of the present invention is based on the discovery that if aketone containing at least two α-hydrogen atoms, as shown by theformula, ##STR5## is halogenated at a temperature in the range ofbetween 0° C. to 50° C. in the presence of an effective amount of amineral acid catalyst, and from 1 to 20 parts per part of said ketone ofa C.sub.(1-8) aliphatic alcohol, that α-haloketone is formedsubstantially free of any polyhalogenated ketone.

There is provided by the present invention, therefore, a process formaking an α-halo ketone based on the halogenation of a ketone of formula(2), which prior to the present invention, resulted in the production ofan α-halo ketone along with significant amounts of poly α-halogenatedketone, which is based on the improvement which comprises,

(1) halogenating the ketone in the range of from 0° C. to 50° C. in thepresence of an effective amount of a Lewis Acid catalyst, or mineralacid catalyst, along with from 1 to 20 parts per part of ketone of aC.sub.(1-8) aliphatic alcohol,

(2) recovering from the mixture of (1), α-halo ketone substantially freeof polyhalogenated ketone.

Included by the ketones of formula (3) are, for example,

acetophenone

propiophenone

deoxybenzoin

p-bromoacetophenone

naphthophenone

p-methoxyacetophenone

desoxyanisoin

diacetylbenzene

2,3-butanedione

2-acetylfluorene

p-acetylbenzenesulfonicacid

acetovanillane

α-acetylanthracene

p-hydroxypropiophenone

p-benzyloxypropiophenone

m-nitroacetophenone

3-(p-methoxybenzoyl)-propionic acid

2',4'-dihydroxy-α-(p-methoxyphenyl)-acetophenone

1,3,5-triacetylbenzene

3,4-dichloroacetophenone

1,4-dibenzoylbutane

β-chloropropiophenone

3-benzoyl-2-phenylpropionitrile

1,4-benzodioxan-6-yl methyl ketone

In addition to providing a route to α-halo ketones, another aspect ofthe present invention is directed to the production of α-halo ketolsbased on the hydrolysis of α-halo ketone. Prior to the presentinvention, one of the methods for making an α-ketol, such as α-hydroxyacetophenone, involved the formation of the acetate derivative ofα-bromo acetophenone, which produced by an acid catalyzedtransesterification of the α-hydroxy acetophenone in 45% overall yield.A further complication of the aforementioned acetate route is that highmolecular weight byproducts formed during the hydroxylation have to beremoved by a purification step. Efforts to directly hydrolyze α-haloketones also presents some difficulty as those skilled in the art knowthat α-halo ketones are quite stable to hydrolysis in slightly acidicmedia unless the hydrolysis is assisted by silver ions. A proceduredescribed by D. J. Lastow et al, J. Amer. Chem. Soc. 87, 1515 (1965)does not provide yields greater than 81% according to gaschromatographic analysis. Interfacial hydrolysis of α-halo ketones, suchas α-bromo acetophenone with sodium hydroxide can result in theproduction of over 20 major products during the reaction. Thesubstitution of a milder base such as sodium carbonate can provideyields as little as 10% of the desired α-ketol.

Another aspect of the present invention is based on the discovery thatα-halo ketones can be readily coverted to α-ketols by effecting thehydrolysis of the α-halo ketone in a water miscible organic solvent,such as acetonitrile, in the presence of an alkali metal salt buffer andan alkali metal salt carboxylic acid promotor such as sodium formate,resulting in quantitative yields of the desired α-ketol.

Accordingly, there is also provided by the present invention, a processfor making an α-hydroxy ketone which comprises,

(1) agitating at a temperature in the range of from about 25° C. to 85°C., a mixture containing as essential ingredients the following:

(A) α-halo ketone,

(B) water miscible organic solvent,

(C) a buffer in the form of an alkali metal salt of a polybasic acidcapable of maintaining the pH of the mixture between about 6.5 to 11,

(D) alkali metal salt of an organic carboxylic acid having a pKa of lessthan about 4,

(E) water,

where there is utilized per mole of (A), at least one equivalent ofalkali metal atoms of (C), at least 0.05 equivalents of alkali metalatoms of (D), and per part of (A), at least one part of (B), and (B) and(E) are employed in the mixture in an amount which is at leastsufficient to provide an equivalent of OH, per halogen atoms of (A),while maintaining a ratio of (B)/(E) having a value of between 0.2 to8.0,

(2) recovering α-hydroxy ketone from the resulting mixture of (1).

The hydrooxadiazinones of formula (1) can be made in accordance with thepractice of the present invention by the following reaction sequence:##STR6##

There is provided by the present invention, therefore, a method formaking a dihydrooxadiazinone which comprises,

(1) halogenating a ketone having at least one α-halogen atom at atemperature in the range of from 0° C. to 50° C. in the presence of aneffective amount of a mineral acid catalyst or a Lewis Acid catalyst andfrom 1 to 20 parts per mole of said ketone of a C.sub.(1-8) aliphaticalcohol,

(2) recovering an α-halo ketone from the mixture of (1),

(3) hydrolyzing the α-halo ketone of (2) by agitating a mixture at atemperature in the range of from 25° C. to 85° C. containing thefollowing as essential ingredients,

(A) α-halo ketones

(B) water miscible organic solvent,

(C) a buffer in the form of an alkali metal salt of a poly basic mineralacid capable of maintaining the pH of the mixture in the range ofbetween 6.5 to 11,

(D) alkali metal salt of an organic carboxylic acid having a pKa lessthan 4, (E) water,

(4) effecting reaction between the resulting α-hydroxy ketone of (3) andan organocarbazate to produce a carbonoorganooxyhydrazone, and

(5) effecting cyclization of the carbonoorganooxyhydrazone in thepresence of an organic solvent to produce a dihydrooxadiazinone.

In the practice of the invention, a ketone having an α-hydrogen atom ishalogenated to convert it to α-halo ketone. The α-halo ketone isthereafter hydroxylated to produce an α-ketol. The α-ketol is condensedwith an organo carbazate to produce a carboalkoxyhydrazone which iscyclized to a dihydrooxadiazinone.

The halogenation of α-hydro ketone is effected by initially forming amixture of the ketone and the alkanol. Although methanol is preferred,suitable alkanols which can also be used are ethanol, propanol, butanol,pentanol, etc. Halogenation of the ketone-alkanol mixture can beinitiated by introducing a small portion of the halogen followed by theintroduction of the acid catalyst. During this period, the mixture isstirred and maintained at a temperature in the range of from 0° C. to50° C. Suitable acid catalysts which can be used are, for example,hydrogen chloride, hydrogen bromide, sulfuric acid, etc., or Lewis Acidcatalysts such as boron trifluoride, aluminum chloride, iron chloride,antimony hexafluoride, tin chloride, etc. The catalysts can be employedin an amount which can vary from 0.1% to 5% based on the weight ofketone. The balance of the halogenating reagent such as bromine can thenbe added. Halogenation can be achieved over a period of from 1.5 to 24hours depending upon the nature of the halogen employed, the temperatureof the mixture and the reactants used, etc. It has been found that ifsubstantially equal molar amounts of halogen and ketone are used,effective results can be achieved. However, from 0.95 moles to 1.05moles of halogen, per mole of ketone also can be employed withoutadversely affecting the overall yield of the reaction.

Prior to recovering the resulting α-halo ketone, it has been founddesirable to introduce into the mixture, a small amount of water tominimize the contamination of the product with enol ethers. Based on themoles of halogen used in the mixture, there can be introduced up to 10mole percent of water at the termination of the halogenation reaction tominimize enol formation. Partial crystallization of the produce canoccur during the initial introduction of water. After the mixture hasbeen cooled to a temperature usually in the range of between about 0° to25° C., excess water can be added to effect the separation of theα-halogenated ketone which may be in the form of crystals or a liquiddepending upon the ketone used. Recovery of the α-halo ketone can thenbe effected by standard means such as filtration, centrifugation, etc.In addition to bromination, additional means of halogenating the ketonesused in the practice of the present invention are for example,chlorination, iodination.

Ketone halogenation can be effectively achieved by the employment of amineral acid catalyst which can be introduced simultaneously orfollowing the introduction of halogen into the mixture of ketone andaliphatic alcohol.

At the termination of the halogenation reaction, up to about 10 molepercent of water based on the moles of halogen employed can be initiallyintroduced which can cause a small degree of precipitation of the α-haloketone. The mixture can then be continuously stirred or agitated bystandard means for a period of 10 to 60 minutes to minimize theproduction of enol ethers which can interfere with the purity of thefinal α-halo ketone. An excess of water then can be added to the mixtureamounting to 150% to 800% by weight, based on the weight of the mixtureto effect the precipitation of the α-halo ketone. Recovery of the finalproduct can be effected by standard means such as by filtration,decantation, etc.

In preparing the α-hydroxy ketone, experience has shown that the orderof addition of the various reactants is not critical. Accordingly amixture of the α-halo ketone with the water miscible solvent, and the"promotor" which hereinafter will refer to an alkali metal salt of anorganic carboxylic acid, such as sodium formate can be initiallyagitated. Water and the alkali metal salt of a polybasic acid can beadded, and the total agitated from a period of from 2 to 60 hours at atemperature in the range of between about 25° C. to 85° C. Upon allowingthe mixture to cool to a temperature of 10° C. to 30° C., separation ofthe α-hydroxy ketone can be readily effected. Recovery of the productdepending upon whether it is a solid or a liquid, can be achieved bystandard techniques. If desired, further purification of the product,such as recrystallization can be effected.

By combining the above-described halogenation step and hydrolysis step,with a subsequent condensation and cyclization step, a total synthesisof the dihydrooxadiazinones of the present invention can be achievedfrom a starting ketone containing an α-hydrogen atom by furthercondensing the α-hydroxy ketone with an organocarbazate followed by thecyclization of the resulting carboorganooxyhydrazone to thedihydrooxadiazinone. The organo carbazate used in the condensation stepcan include for example, methyl carbazate, ethyl carbazate, phenylcarbazate, isopropyl carbazate, butyl or isobutyl carbazate,ethylenebiscarbazate, phenylenebiscarbazate, etc. The condensation canbe effected at temperatures in the range of between about 20° C. to 60°C. Substantially equal molar amounts of the α-hydroxy ketone, which canexist in solution from the above hydrolysis reaction and the organocarbazate can be stirred when the mixture is maintained at a pH of about4 to 6 which can be achieved by adding to the mixture a mineral acidsuch as hydrochloric acid or sulfuric acid. The condensation reactioncan be effected at a temperature of from 20° C. to 60° C. over a periodof from about 2 to 24 hours. Recovery of the carboorganooxyhydrazone canbe effected by gravity separation techniques such as filtration, etc.,and the product washed with water and dried by standard means.

The cyclization of the carboorganooxyhydrazone can be achieved byheating it with an organic solvent such as toluene. There can be added acyclization catalyst such as anhydrous potassium carbonate, sodiumcarbonate, sodium hydride, sodium alkoxide, etc. The dihydrooxadiazinonecan be recovered by allowing the mixture to cool thereafter washing thefinal product with an organic solvent or hot water and drying bystandard means such as a vacuum oven at temperatures in the range ofabout 70°-80° C. It has been found as a practice that thecarboorganooxyhydrazone can be dried by azeotropic distillation underreduced pressure prior to the addition of the cyclization catalyst.

The dihydrooxadiazinones which can be made in accordance with thepractice of the present invention, can be used as blowing agents in avariety of thermoplastic organic polymers as shown in my copendingapplication Ser. No. 669,028, filed Mar. 22, 1976 and assigned to thesame assignee as the present invention. A proportion of from about 0.1to 1.0 percent of blowing agent, based on the weight of the plastic willprovide for effective results. Incorporation can be achieved by standardmelt extrusion techniques based on the particular decomposition point ofthe blowing agent and the melt extrusion characteristics of thethermoplastic polymer.

In order that those skilled in the art will be better able to practicethe invention, the following examples are given by way of illustrationand not by way of limitation. All parts are by weight.

EXAMPLE 1

There was added 5 parts of bromine to a mixture of 120.15 parts ofacetophenone and 190 parts of methanol, which was being stirred duringthe addition. The temperature of the mixture was maintained at about10°-15° C.; anhydrous hydrogen bromide was then introduced into thereaction solution until the bromine color disappeared. An additionalamount of bromine was then introduced over a 2 hour period to produce amixture to which an equal molar amount of bromine per mole ofacetophenone had been added. After the bromine had been added, 18 partsof water was introduced which amounted to about 100 mole percent ofwater based on the moles of bromine added. The reaction mixture was thencooled to a temperature of from 0° C.-15° C. An excess of wateramounting to about 1300 parts was then added over a 15 minute periodwith stirring to effect the precipitation of α-bromo acetophenone whichseparated as fine white crystals. The crystals were collected on afilter paper and rinsed with water. Based on weight of reactants theyield of product was about 96% having a purity of greater than 99.9%.

EXAMPLES 2-6

The procedure of Example 1 involving halogenating with bromine wasrepeated except that in particular instances the alcohol used was variedor the ketone was varied. The results shown are as follows:

                  TABLE I                                                         ______________________________________                                                                          % Yield                                     Example Alcohol       Ketone      (isolated)                                  ______________________________________                                        2       methanol   deoxybenzoin   >95                                         3       methanol   propiophenone  >95                                         4       ethanol    acetophenone    98                                         5       isopropyl  acetophenone   >95                                         6       methanol   p-bromoacetophenone                                                                           95                                         ______________________________________                                    

The procedure of Examples 1-6 was repeated except that in place ofC.sub.(1-8) aliphatic alcohol there was used acetonitrile as thesolvent. The temperature of the mixture was maintained between 0° to 5°C. during the bromination. There was obtained a mixture containing about67% of α-bromo acetophenone which was significantly less than thequantitative yield achieved by use of a C.sub.(1-8) aliphatic alcohol inaccordance with the practice of the present invention. In addition toacetonitrile, acetic acid and methylene chloride were used assubstitution for the C.sub.(1-8) alcohol at the same or substantiallythe same molar concentration as employed in Examples 1-6 above. Theα-bromo acetophenone obtained at 0° to 5° C. with acetic acid was about61.6% and that obtained with methylene chloride was about 67.8%. Basedupon these results, one skilled in the art would know that the resultsachieved by the use of a C.sub.(1-8) aliphatic alcohol were quiteunexpected with respect to yield of α-halogenated ketone.

EXAMPLE 7

There was added 151.9 parts of sodium bicarbonate and about 600 parts ofwater to a mixture at a temperature of 50° C. while it was stirred of300 parts of α-bromo acetophenone, 104.5 parts of sodium formate andabout 700 parts of acetonitrile. The resulting mixture was stirredvigorously for 16 hours at 60° C. during which time carbon dioxideevolved. After cooling the reaction mixture, the acetonitrile solutionwas separated from the aqueous layer and evaporated to dryness toproduce 97.5% of a crystalline product. The material was furtherpurified by recrystallization from water resulting in the production ofα-hydroxy acetophenone hydrate having a melting point in the range of73°-76° C. The final yield of the isolated product was 72.5%.

Further studies were made on the hydrolysis of α-bromo acetophenoneemploying the method of Example 7, except that in certain instances theamount of sodium formate was varied or prepared in situ or the amount ofsodium bicarbonate in acetonitrile were varied. Acetonitrile was variedover a range of from about 0.3 moles per liter up to about 0.9 moles perliter of reaction mixture. In addition to sodium bicarbonate, sodiumcarbonate was also used as an acid acceptor. The results obtained areshown as follows in Table II covering Examples 8-14 where percent yieldsof α-hydroxy acetophenone hydrate are based on peak areas using gaschromatographic analysis.

                  TABLE II                                                        ______________________________________                                                        Acid                                                                          Acceptor    Promotor                                          Ex.   Solvent   (equiv.)    (equiv.)  % Yield                                 ______________________________________                                         8    acetonitrile                                                                            Na.sub.2 Co.sub.3                                                                      (1.0)                                                                              --        27                                     9    "         NaHCO.sub.3                                                                            (1.2)                                                                              --        81.4                                  10    "         "        (1.3)                                                                              HCO.sub.2 Na (1.03)                                                                     >99.9                                 11    "         "        (2.0)                                                                              HCO.sub.2 Na (0.1)                                                                      88                                    12    "         "        (1.6)                                                                              HCO.sub.2 H (0.25)                                                                      99                                    13    "         "        (2.0)                                                                              HCO.sub.2 H (0.4)                                                                       99.3                                  14    methanol  "        (1.2)                                                                              HCO.sub.2 Na (1.0)                                                                      97.5                                  ______________________________________                                    

Examples 8-14, above, indicate that an unexpected effect is achieved bythe use of sodium formate as a promoter either as a salt or prepared insitu. The temperature of the reaction using sodium carbonate as anacceptor was 45° whereas results shown for sodium bicarbonate are basedon a reaction temperature of 60°-65°. A significant result is also shownwith respect to the amount of sodium formate used based on itsequivalence present in the mixture and the percent yield of theα-hydroxyacetophenone.

EXAMPLE 15

There was added 10.08 parts of sodium bicarbonate and about 60 parts ofwater to a mixture of 21.3 parts of α-bromopropiophenone, 6.8 parts ofsodium formate and about 90 parts of acetonitrile. The resulting mixturewas stirred vigorously for 48 hours at 65° C. during which time carbondioxide evolved. After cooling, the acetonitrile solution was separatedfrom the aqueous layer and evaporated to dryness. The residue wasdissolved into chloroform which was extracted once with water, driedover sodium sulfate, and evaporated to produce analytically pure (>98%)α-hydroxypropiophenone. The yield of this isolated product was 77.1%.

EXAMPLE 16

About 13 parts of bromine was added with stirring to a mixture of 474.6parts of acetophenone in about 640 parts of methanol, while the mixturewas stirred and maintained at a temperature between 5°-10° C. Hydrogenbromide gas was then introduced into the mixture until brominecoloration disappeared, at which point an additional amount of brominewas added over a 2 hour period to make a total of 631.3 parts. There wasthen added 71 parts of water while the mixture was stirred andexternally cooled for a period of about 30 minutes. An excess of about2700 parts of water was then slowly added to effect the precipitation inthe form of crystals of α-bromo acetophenone from the mixture. Thecrystals were decanted by means of a vacuum siphon, washed, thenneutralized with a 20% sodium hydroxide solution and decanted todryness. There was then added about 940 parts water, 1600 parts ofmethanol, 333 parts of sodium bicarbonate and a sodium formate solutionprepared from 161 parts of 90% formic acid and sufficient sodiumhydroxide to neutralize the acid. The mixture was heated at 60° C. withvigorous stirring for 7 hours after which time it was cooled to ambienttemperature and filtered. Based on method of preparation and gaschromatographic analysis of the mixture there was produced α-hydroxyacetophenone in quantitative yields.

Dilute hydrochloric acid was added to the mixture of the above filtratewith 855.8 parts of methyl carbazate which had been prepared fromequivalent amounts of hydrazine and dimethyl carbonate. Sufficienthydrochloric acid was used to provide a pH of 5.5 after which themixture was stirred at 38° C. for 6 hours. A crystalline precipitate wasformed which was filtered from the mixture and washed with water. Basedon method of preparation and spectroscopic analysis the product was thecarbomethoxy hydrazone of α-hydroxy acetophenone.

A mixture of the above carbomethoxyhydrazone and about 1,900 parts oftoluene was refluxed under reduced pressure to effect the removal ofresidual water from the crystalline product. There was then added 10parts of anhydrous potassium carbonate to the mixture and the heatingwas continued under reduced pressure until all of the methanol-tolueneazeotrope was removed. The mixture was then allowed to cool to producethe above-described blowing agent5-phenyl-3,6-dihydro-1,3,4-dihydrooxidiazin-2-one which was finallydried in a vacuum oven at 70°-80° C. The overall yield of final productwas 456 parts which represented a 65.5% yield based on acetophenone. Themelting point of the product was 163.165° C.

Dry powder blends of a bisphenol-A polycarbonate resin powder having anintrinsic viscosity on the average of about 0.55 dl/g and a density ofabout 1.17 with the above described blowing agent of the presentinvention and a commercially available blowing agent isopropyl hydrazodicarboxylate were prepared consisting respectively of 0.6 part ofblowing agent per 100 parts of the polycarbonate resin. Thepolycarbonate resin was in the form of a finely divided powder which hadbeen dried at 125° C. for 16 hours. The aforementioned blends were meltextruded at temperatures in the range of from about 282° C. to 305° C.During melt extrusion thermoplastic foam was formed from theaforementioned finely divided dry blends. In addition to melt extrudingthe aforementioned foamable blends there was also melt extruded the samepolycarbonate resin free of blowing agent. The density (g/cc) of therespective blends and the resin free of the blend was measured over therange of between 282° C. to 305° C. The intrinsic viscosities inchloroform of the polycarbonate resin and the polycarbonate resin andthe aforementioned blends was also measured for the samples which weremelt processed over the range of between 282° C. to 322° C. to determinethe reduction in molecular weight if any during the foaming process as aresult of polymer degradation. The following table shows the resultobtained, where "T" is in ° C., "Density" shows the change effected overa temperature as a result of "foaming", "IV" shows the change inintrinsic viscosity if any, of the polycarbonate resin as a result ofpolymer degradation due to byproducts of the blowing agent, where BlendA contains the dihydrooxadiazinone in accordance with the presentinvention and Blend B contains the isopropyl hydraodicarboxylate:

                  TABLE III                                                       ______________________________________                                                Density                                                                         Poly                                                                T (° C.)                                                                         carbonate  Blend A     Blend B                                      ______________________________________                                        282       1.17       1.18        1.15                                         293       --         1.03        0.82                                         299       --         --          0.80                                         305       1.13        .86        0.70                                         316       1.14       --          --                                           321       --         --          --                                           ______________________________________                                    

Table III shows that the dihydrooxadiazinone of the present inventioncan be used effectively as a foaming agent for thermoplastic organicresin without significantly degrading the thermoplastic organic resin asa result of the foaming process. The isopropylhydrazodicarboxylate ofthe prior art shows a 15% change in the intrinsic viscosity of thepolymer indicating that significant polymer degradation has occurred.

EXAMPLE 17

A mixture of 15.53 parts of p-bromophenylhydroxymethylene ketone, about140 parts of absolute methanol and 6.49 parts of methylcarbazate wasstirred and there was added dropwise to the mixture sufficient formicacid to produce a final mixture having a pH of 5.5. The mixture was thenheated to 40° C. and allowed to stir at ambient conditions for 12 hours.There was obtained 17.1 parts of an adduct as follows: ##STR7## whosemelting point was 175.9° C. The above product was then recrystallizedfrom acetone and water resulting in a material having a melting point of181.5° C. which was submitted for IR and elemental analysis. Theidentity of the product was confirmed by elemental analysis.

A mixture of about 90 parts of benzene, 12.4 parts of the above adductwas refluxed until a constant head temperature of about 78° C. wasmaintained. The mixture was then allowed to cool to room temperature andabout 2 parts of K₂ CO₃ was added. The mixture was then refluxed for 5hours to effect the removal of benzene-methanol azeotrope. The mixturewas then allowed to cool and filtered of solids. There was obtained 9.3parts of product. The product was then recrystallized from acetone andwater and dried in a vacuum oven. The product has a melting point of184°-7° C. Based on method of preparation, IR spectrum and elementalanalysis, the product had the formula, formula, ##STR8##

The above dihydrodiazinone was found to have a decomposition temperaturein the range of about 240°-260° C. In accordance with the procedure ofExample 16, it is dry blended with bisphenol-A polycarbonate to producea mixture of about 0.6 part of blowing agent per 100 parts ofpolycarbonate resin. The resulting blend is melt extruded in the rangeof about 280° C. to 310° C. to produce a foam substantially similar tothe foam made in Example 16 using the dihydrodiazinone of the presentinvention.

EXAMPLE 18

A mixture of about 70 parts of methanol, 17 parts of 2'-aceto-naphthoneand 16 parts of bromine was stirred. There was added 1 equivalent ofwater to the resulting mixture to effect the crystallization of product.An additional 400 parts of water were added and the stirring of themixture was continued for about 1 hour. There was obtained 33.15 partsof product having the formula, ##STR9## The product was found to have amelting point of 72°-75° C. It was then recrystallized from ethanol toproduce product having a melting point of 80°-82° C. The identity of theabove product was further confirmed by NMR and IR. The final yield ofthe recrystallized product was 19.46 parts.

A mixture of 18.46 parts of the above product, 5.03 parts of sodiumformate and about 70 parts of acetonitrile was heated and stirred to atemperature of about 60° C. for 1 hour. There was then added to themixture, 6.3 parts of sodium bicarbonate and about 45 parts of water.The temperature of the mixture was then raised to 65° C. The mixture wasthen stirred for 43 hours to complete the reaction. There was obtained ayield of 14.58 parts of product from the organic layer which had beenfiltered having a melting point of 90°-98° C. The product was thenrecrystallized from acetone and water to provide 7.1 parts of a producthaving a melting point of 113°-115° C. The identity of the product wasas follows: ##STR10## which was confirmed by its IR spectrum andelemental analysis.

A mixture of about 100 parts of absolute methanol, 7.78 parts of theabove naphthyl ketone and 3.78 parts of methyl carbazate were mixted andstirred together. To the resulting mixture there was added a few dropsof formic acid to adjust the pH of the mixture to 5.5. The mixture wasthen heated to 40° C. and allowed to stir for an additional 12 hours atambient temperatures. There was obtained 6.75 parts of a naphthylenederivative having the formula, ##STR11## having a melting point of162°-6° C., whose identity was confirmed by its IR spectrum andelemental analysis.

A mixture of 3.6 parts of the above naphthyl semicarbazate derivativeand about 50 parts of benzene was stirred and refluxed until the headtemperature was maintained at about 78° C. The mixture was then allowedto cool and additional potassium carbonate was added. The mixture wasthen heated to reflux and the heating was continued until all of themethanol-benzene azeotrope had been removed. The mixture was then cooledand filtered to produce 4 parts of product which was recrystallized fromacetone and water. There was obtained a final yield of 2.5 parts afterrecrystallizing from acetone and water and drying in an oven. Based onmethod of preparation and its NMR spectrum the product had the formula,##STR12## The product was found to decompose at a temperature in therange of from 225° C. to 250° C. In accordance with the procedure ofExample 16, the product is dry powder blended with bisphenol-Apolycarbonate. It is then melt extruded in the range of from 260° C. to300° C. It is found that the above blowing agent can provide a valuableshaped foam structure when foamed in accordance with the teaching of thepresent invention.

Although the above examples are directed to only a few of the very manyvariables included by the method of the present invention as well as thedihydrooxadiazinones, it should be understood that the present inventionincludes the parameters shown in the description proceding theseexamples as well as dihydrooxadiazinones as shown by formula (2). Amongthe preferred dihydrooxadiazinones of formula (1) are compounds havingthe formula, ##STR13## where R⁴ is a monovalent C.sub.(6-13) aromaticorganic radical selected from aryl radicals, halogenated aryl radicals,alkoxy aryl radicals, nitro aryl radicals and sulfoaryl radicals.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:
 1. Dihydrooxadiazinones of the formula, ##STR14## where "a"is an integer equal to 1 or 2, and when "a" is 1, R³ is a monovalentradical and when "a" is 2, R³ is a divalent radical, and R³ is selectedfrom the class consisting of aryl radicals selected from the classconsisting of tolyl, xylyl and naphthyl, halogenated aryl radicalsselected from the class consisting of halophenyl, halotolyl, haloxylyland halonaphthyl, alkoxy aryl radicals selected from the classconsisting of alkoxy phenyl, alkoxy tolyl, alkoxy xylyl and alkoxynaphthyl, nitroaryl radicals selected from the class consisting of nitrophenyl, nitro tolyl, nitro xylyl and nitro naphthyl, sulfoaryl radicalsselected from the class consisting of sulfo phenyl, sulfo tolyl, sulfoxylyl and sulfo naphthyl, arylene radicals and halogenated aryleneradicals.
 2. Dihydroxadiazinone of the formula, ##STR15## where R⁴ is amonovalent C.sub.(6-13) aromatic organic radical selected from arylradicals selected from the class consisting of tolyl, xylyl andnaphthyl, halogenated aryl radicals selected from the class consistingof halo phenyl, halo tolyl, halo xylyl and halo naphthyl, alkoxy arylradicals, nitro aryl radicals selected from the class consisting ofnitro phenyl, nitro tolyl, nitro xylyl and nitro naphthyl and sulfoarylradicals selected from the class consisting of sulfo phenyl, sulfotolyl, sulfo xylyl and sulfo naphthyl.
 3. The compound5-bromophenyl-3,6-dihydro-1,3,4-oxadiazin-2-one.
 4. The compound5-naphthyl-3,6-dihydro-1,3,4-oxadiazin-2-one.